Nonminimal coupling and quintessence - art. no. 064007

Recent studies of type Ia supernovas with redshifts up to about z less than or similar to 1 reveal evidence for a cosmic acceleration in the expansion of the Universe. The most straightforward explanation to account for this acceleration is a cosmological constant dominating the recent history of ou r Universe; however, a more interesting suggestion is to consider an evolvi ng vacuum energy. Several proposals have been put forward along these lines , most of them in the context of general relativity. In this work we analyz e the conditions under which the dynamics of a self-interacting Brans-Dicke field can account for this accelerated expansion of the Universe. We show that accelerated expanding solutions can be achieved with a quadratic self- coupling of the Brans-Dicke field and a negative coupling constant omega.